The field of this invention is a releasing system for downhole packers and more particularly, a system where the release mechanism is protected from accidental release and damage from flowing fluids.
In the past, downhole packers were released in three different ways. Dogs were unsupported to let the body be extended for release. Collets became unsupported to have the same effect. Finally, the packer could be cut downhole to allow release. FIGS. 1a-1c illustrate a prior art mechanically set packer with a collet release system. A setting tool (not shown) pushes down on setting sleeve 10 while pulling up on the top sub 12 of mandrel 14. The setting sleeve 10 pushes down on the sealing elements 16, the upper cone 18 and the slips 20, while the mandrel 14, through collets 22, pulls up on the lower cone 24. The set position is held by body lock ring 26, which works like a ratchet to keep the set packer from relaxing. As seen in FIGS. 1c and 2, a support sleeve 28 is held on to the collets 22 by shear pins 30. In the position shown in FIG. 1c the support sleeve transmits the upward pull force from the top sub 12 to the lower cone 24 during the setting procedure. To release the packer, a release tool (not shown) is run downhole to engage the support sleeve 28 and pick it up so as to break shear pins 30 and to undermine the contact between the collets 22 and bottom sub 32 (see FIG. 3). The releasing tool brings up the support sleeve 28 against the mandrel 14 to allow the slips 20 to be undermined as the upper cone 18 is pulled out from under them. In a similar manner, the elements 16 are allowed to relax.
In a similar manner, the prior art design of FIGS. 4 and 5 operated to allow the packer to set and, later, to release, when a release tool (not shown) moved up release sleeve 34 undermining the segmented dogs 36 for a release from the bottom sub 38. These structures were also used with hydraulically set packers.
The potential problem with these designs is the exposed placement of the support sleeve 28 or the release sleeve 34. Lowing well fluids can cause damage due to erosion or corrosion. Additionally, tools are frequently run through such packers to actuate other devices below the packer. These tools could, inadvertently, engage the support sleeve 28 or the release sleeve 34 and trigger a release of the packer. This problem could be avoided with another known design which requires the packer to be cut loose after being set downhole. This technique is complicated and requires very experienced personnel to perform the operation. This technique also generates cuttings which can be left in the well and the packer is destroyed in the process, preventing reuse.
The present invention presents a unique mechanism for release which overcomes the drawbacks of the prior art as described above. The release mechanism is minimally exposed to the wellbore to give it protection from well fluid attack and accidental release from contact by other tools. Additionally, the packer is simply released and can be reused. These and other advantages of the present invention will be more readily understood from a review of the description of the preferred embodiment, which appears below. Other known packer release designs are illustrated in U.S. Pat. Nos.: 3,311,171; 3,361,207; 3,976,133; 4,216,827; 4,436,150; 4,518,037; 4,565,247; 4,664,188; 5,333,685; 5,718,291; and 5,787,982.
A release system for a packer is disclosed. The release ring is minimally exposed in the wellbore and is actuated by a release tool, which comprises a collet and cone with a relative movement feature. In the preferred embodiment, the release ring has alternating cuts and a built in radially outward bias. The ring is held in locked position by bands, which are broken by the action of the releasing tool.